1. Field of the Invention
This invention relates generally to the construction and operation of acoustic signal generators, especially of the marine gas exploder type wherein a gas explosion confined in an expansible chamber acts to create an acoustic pulse by moving a mass through the water. Specifically, the invention relates to a means and a method for expelling gas and liquid combustion products from such a combustion chamber in a single step.
2. Description of the Prior Art
Acoustic signal sources such as underwater seismic gas exploders are typically operated by ignition of an explosive gas mixture confined within a combustion chamber separating two relatively movable rigid bodies. Movement of at least one of these bodies is adapted to propel a mass through the water at a rate sufficient to generate an acoustic signal.
In prior art apparatus of this character, oxygen and propane are introduced into the combustion chamber of an underwater cylinder under suitable pressure and there ignited with a conventional spark plug. The resultant combustion products are expelled through an exhaust tube communicating with the chamber.
It is recognized that there will always be some residual condensation present in such a combustion chamber. The main reason for this is that water is one by-product of the chemical reaction of oxygen and propane. Since the underwater environment is being constantly cooled, some of this water, initially in the form of steam, condenses along the walls of the cylinder after each firing. This condensation causes a pressure drop within the chamber; and if the exhaust line is vented to the atmosphere, outside air will be sucked in to equalize the differential pressure. This introduces a further source of water vapor and condensate. If not removed from the combustion chamber, all such condensate will accumulate and may splash against the spark plug causing it to misfire and eventually occupy sufficient space to significantly reduce the force of succeeding explosions.
One prior art technique for extracting such condensate is illustrated in U.S. Pat. No. 3,509,962. In this patent, liquid products of combustion within a seismic marine gas exploder are gathered at the lower inclined end of a combustion chamber and thereafter passed through a siphon which feeds into the flow of exhaust gases in an exhaust line. Ejection of condensed liquids in this manner occurs only during the maximum pressure phase of the combustion, and it appears that continuous vacuum must be applied to the exhaust line in order to suck out the atomized liquid.
It is therefore a general object of this invention to provide an apparatus for removal of condensate from the combustion chamber of a marine gas exploder.
It is a more specific object of this invention to provide an apparatus of the character described in which such condensate is removed automatically responsive to the flow of gaseous combustions products from said chamber.
It is a still further object of this invention to provide an apparatus of the character described in which such condensate may be removed automatically at any of several phases of the operation of such apparatus.